Metal-oxide-semiconductor (MOS) transistor is one of the most important components in modern integrated circuits. The basic structure of the MOS transistor includes a semiconductor substrate, a gate structure formed on the semiconductor substrate, and source and drain doped regions formed in the semiconductor substrate on both sides of the gate structure. The gate structure includes a gate dielectric layer formed on the semiconductor substrate, and a gate electrode layer formed on the gate dielectric layer.
With the development of semiconductor technology, the control capability of the conventional planar MOS transistor on the channel current is reduced, causing a serious leakage current. A fin field effect transistor (FinFET) is one of emerging multifaceted-gate devices. The FinFET generally includes one or more protruding fins formed on a substrate, a gate structure across a length portion of the fins and covering a portion of a top surface and sidewalls of each fin, and source and drain doped regions formed in the fin on both sides of the gate structure.
Fins having different widths need to be formed to meet the requirements of different functional devices. For example, width of the fin of the FinFET needs to decrease to reduce a short-channel effect. In a varactor diode, to improve the quality factor, width of the fin of the varactor diode needs to increase to reduce the resistance of the fin in the varactor diode.
However, conventional methods for forming the fins having different widths are complicated. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.